U.S. actor Philip Seymour Hoffman poses on the red carpet during a screening for the movie "The master" at the 69th Venice Film Festival in Venice September 1, 2012. (REUTERS/MAX ROSSI)

Oscar-winning actor Philip Seymour Hoffman, known for his lead role in film "Capote," was found dead - with a hypodermic needle still stuck in his arm - on Sunday at his Greenwich Apartment in Manhattan. He was 46 years old.

Screen writer and friend David Bar Katz called police around 11:30 a.m. after he and a female friend found Hoffman unconscious in his underwear on the bathroom floor, sources told the New York Post.

Katz and his friend went to check on Hoffman after he missed the time to pick up his three children that he had with Mimi O'Donnell, his partner for 15 years, the New York Post reports.

Investigators found eight empty envelops containing what were believed to be heroin scattered throughout the actor's apartment, police said. "He was shooting up in the bathroom."

Hoffman's family expressed their shock and grief through a statement, and ask the public to keep Phil in their thoughts and prayers.

"We are devastated by the loss of our beloved Phil and appreciate the outpouring of love and support we have received from everyone," the statement reads. "This is a tragic and sudden loss and we ask that you respect our privacy during time of grieving."

Shortly after news of Hoffman's death broke, those who knew of the Academy Award actor personally and those who only knew him through his movies poured their condolences to his family.

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Hoffman was born in upstate New York near Rochester. He began his career in 1991 in an episode of Law and Order, and later appeared in classic movies including The Big Lebowski, The Talented Mr. Ripley, Moneyball.

He is best known for his Oscar-winning role for the 2005 biographical film Capote, in which he played writer Truman Capote. His other performances that had won Academy Award nominations include the following top movie roles:

Scotty J., Boggie Nights (1997)

Allen, Happiness (1998)

Lester Bangs, Almost Famous (2000)

Truman Captoe, Capote (2005)

Gust Avrakotos, Charlie Wilson's War (2007)

Lancaster Dodd, The Master (2012)

Gunther Bachmann, A Most Wanted Man (2013)

Hoffman admitted in interviews last year to have redeveloped heroin addiction after being sober for 23 year, which led to a stint at a rehabilitation center.

In the last decade, he was vocal about his drug abuse addictions, which haunted him for more than half of his life. His first episode of bout against serious addiction was in 1989 after graduating from New York University.

"It was all that drugs and alcohol, yea," he told 60 Minutes in 2006. "It was anything that I could get my hands on... I liked it all."

Hoffman was eventually able to control his addiction and lived sober for the next 23 years, but he succumbed to the same demons. In May 2013, he checked himself into rehab for heroin abuse.

Hoffman had been shooting "The Hunger Games: Mockingjay - Part 2" at its prime and was in post-production for the Showtime series "Happyish."